Spark plug with improved seal between the shell and insulator



June 21, 1966 L. R. LENTZ ETAL SPARK PLUG WITH IMPROVED SEAL BETWEEN THE SHELL AND INSULATOR Filed Feb. 5, 1964 INVENTORS Mwmmcz P. LEA/T2 & BYfi/EODOAE ,4. KOsm/H? 4T7'0/PA/EY5 United: States Patent 3,257,503 SPARK PLUG WITH IMPROVED SEAL BETWEEN THE SHELL AND INSULATOR Lawrence R. Lentz and Theodore A. Kosydar, Toledo, Ohio, assignors to Champion Spark Plug Company, Toledo, Ohio, a corporation of Delaware Filed Feb. 5, 1964, S'er. No. 342,716 6 Claims. (Cl. 174-452) This invention relates to a spark plug for igniting gases in a chamber containing gases under high pressure, and more particularly to a spark plug for use in high pressure gas engines. f

With the use of high-output, industrial gas engines, it has been found that the high pressures associated with compression and explosion in such engines will occasionally blow the insulator core assembly out of a shell of a spark plug used in the engine. Even where this does not occur, it is not uncommon for the spark plugs to develop leaks after a relatively short period of operation which soon destroy the elements of the spark plug.

The present invention provides an improved spark plug or the like which has a strong mechanical connection between the spark plug shell and the insulator to virtually eliminate the possibility that the insulator can be physically blow from the shell. At the same time, the new spark plug employs an effective gas seal between the insulator and the shell which will not fail due to expansion and contraction of the spark elements or because of fluctuation in the engine pressure which tends to pulsate the spark plug elements and eventually loosen the seals.

It is, therefore, a principal object of the invention to provide an improved, more durable spark plug for use in gas engines or the like in which the spark plug is subjected to very high cylinder pressures.

Many other objects and advantages of the invention will be apparent from the following detailed description of a preferred embodiment thereof, reference being made to the accompanying drawing, in which:

FIG. 1 is a view in longitudinal cross section of a spark plug embodying the invention;

FIG. 2 is a bottom view of the spark plug of FIG. 1; and

FIG. 3 is a fragmentary, enlarged view of a portion of the spark plug shown in dotted lines in FIG. 1.

Referring to the drawing, and more particularly to FIG. 1, a spark plug embodying the invention is indicated generally by the reference numeral and basically includes an outer metal shell 12 having ground electrodes 14 and a core assembly including an insulator 16 carrying a center composite electrode 18, the details of which form no part of the instant invention. The outer metal shell 12 has, conventionally, a lower external thread 20 at its firing end to connect the spark plug 10 into a threaded opening in a cylinder head of a gas fueled, high output engine. The shell 12 also has a longitudinally extending passage therethrough comprising a small diameter portion 22 and a large diameter portion 24, with the large diameter portion 24 having an internal thread 26 located near the end of the shell 12 opposite the end with the external thread 20. The small diameter portion 22 has an internally-extending shoulder 28 formed therein which receives the insulator16.

The insulator 16 has a lower shoulder 30 seating on the shell shoulder 28 with a gasket 32 therebetween. The gasket 32 provides a first effective seal against leakage of high pressure gases from the engine when the gasket is compressed between the shoulders 28 and 30. The insulator 16 also has an intermediate shoulder 34 located in the large diameter portion 24 of the shell passage and an upper shoulder 36 of smaller diameter than the shoulder 34. A body of compressible holding and sealing powder 38 is placed in an annular space or pocket between the insulator shoulders 34 and 36 and between the insulator 16 and the large diameter passage portion 24 of the shell 12. A first sealing ring 40 is placed around the insulator 16 against the intermediate shoulder 34 before the powder 38 is added, after which the powder 38 is tamped to maintain it in place. The body of holding and sealing powder 38, when compressed, in combination with the sealing ring 40 and the intermediate shoulder 34, provide an effective second seal against the flow of high pressure gases from the engine chamber. However, the intermediate shoulder 34 may not be absolutely essential since the powder could be placed between the internal shoulder 28 of the shell and the upper shoulder 36 of the insulator 16. The intermediate shoulder 34 does enable the use of less of the powder 38 and also provides a better seal than otherwise. The powder 38 is of a known resilient type, which is described more fully in Patent No. 2,020,- 967, for example, and forms an effective gas seal when compacted.

After the body of compressible powder 38 is added to the annular space, the powder is tamped and reamed until the upper end forms a smooth surface. An asbestos packing or compression means 41 is then placed on top of the powder 38,'after which an annular force distribution, or second sealing ring 42, which is wider but thinner than the sealing ring 40, is placed on the upper shoulder 36 and the gasket 41. The gasket 41 is not essential but enables a larger Compression force to be placed on the powder 38 than is otherwise possible.

An annular member or gland nut 44 is located above the upper shoulder 36 and has an external thread 46 which threadedly engages the internal thread 26 of the shell 12. The gland nut. 44 also has a non-circular, upper end 48 by which the nut is seated. A lower end 50 of the gland nut 44 has a surface contoured similarly to the surface of the upper shoulder 36 and the gasket 41, when compressed, and moves toward both as the nut is turned downwardly. Pressure is thereby placed on both the shoulder 36 and the body of powder 38 through the ring 42 and the gasket 41 by means of the nut 44. This holds the insulator securely in place and still enables a secure heat conductive gas seal to be effected by means of the gasket 32 and also by means of the powder 38 and the associated gasket 41 and the rings 41) and 42.

Various modifications of the above described embodiment of the invention will be apparent tothose skilled in the art, and it is to be understood that such modifications can be made without departing from the scope of the invention, if they are within the spirit and the tenor of the accompanying claims.

We claim:

1. A spark plug comprising an outer metal shell having an external thread near its firing end to engage a spark plug opening in a wall of an engine cylinder containing gases under high pressures, said shell also having a central passage therethrough including a large diameter portion and a smaller diameter portion, an internal thread in the large diameter portion of said passage near the end of said shell opposite the firing end, a shoulder in said small diameter portion of said passage near said firing end, an insulator extending substantially through said passage and having a lower shoulder cooperating with said shell shoulder to limit movement of said insulator toward said firing end, said insulator also having an intermediate shoulder and an upper shoulder, said intermediate and upper shoulders facing opposite said lower shoulder, a lower gasket between said shell shoulder and said lower shoulder of said insulator, a first sealing ring of deformable material above said intermediate shoulder bridging the space between said shell and insulator, a body of compacted resilient sealing and holding powder above said sealing ring between said ring and a point below said upper shoulder and between said insulator and said large diameter portion of said passage, an upper packing above and in contact with said powder, a second annular force distribution ring above said upper shoulder with a radially inner portion bearing on said upper shoulder and a radially outer portion bearing on said packing, and a gland nut above said upper shoulder and said upper gasket and around said insulator, said nut having an external thread threadedly engaged with said internal thread of said shell, said nut having an upper non-circular end portion above said shell, and said nut having a lower end bearing against said annular force distribution ring to distribute force on said upper shoulder of said insulator and said upper packing when said nut is turned downwardly whereby said nut forces said insulator downwardly to squeeze said lower gasket between said lower shoulder and said shell shoulder to provide a heat conductive path out of said insulator and said nut also places pressure downwardly on said powder to resiliently force said first sealing ring against said intermediate shoulder and said shell to provide sealing means to inhibit escape of high pressure gases from the chamber.

2. A spark plug comprising an outer metal shell having an external thread near is firing end to engaged a spark plug opening in a wall of an engine cylinder containing gases under high pressures, said shell also having a central passage therethrough, an internal thread in said passage near the end of said shell opposite said firing end, a shoulder in said passage near said firing end, an insulator extending substantially through said passage and having a lower shoulder cooperating with said shell shoulder, said insulator also having an upper shoulder, said upper shoulder facing opposite said lower shoulder and sloping downwardly and radially outwardly, said insulator and said shell forming a pocket positioned below said upper shoulder and which pocket is substantially closed at its lower end, a lower heat conductive metal gasket between said shell shoulder and said lower shoulder of said insulator, a sealing ring in said pocket above the closed end thereof, compacted powder above said sealing ring in said pocket, packing above and in contact with said powder, an annular force distribution ring above said upper shoulder and said packing, and a gland nut above said force distribution ring, said nut having an external thread threadedly engaged with said internal thread of said shell, said nut having an upper non-circular end portion above said shell, and said nut having a lower end contoured to cooperate with said annular force distribution ring to press said annular force distribution ring against said upper shoulder of said insulator and against said packing when said nut is turned downwardly, wereby said nut forces said insulator downwardly to squeeze said lower gasket between said lower shoulder and shell shoulder and said nut also places pressure downwardly on said powder to force said first sealing ring against said intermediate shoulder to provide sealing means to inhibit escape of high pressure gases from the chamber.

3. A spark plug comprising: an outer metal shell having a central passage therethrough, said shell having a shoulder in said passage near the lower end, an insulator extending substantially through said passage and having a lower shoulder for transferring abutment force to said shell shoulder, said insulator also having an upper shoulder facing opposite said lower shoulder, said insulator and shell forming a pocket position below said upper shoulder and which pocket is subst-antialy closed at its lower end, a body of packing powder in said pocket, an annular force distribution ring above said upper shoulder and overlying said powder with the radially inner portion of said annular ring arranged to apply compressive force ot said insulator and the radially outer portion of said annular ring arranged to apply compressive force to said powder, a sealing ring closing off the bottom of said pocket beneath said powder, and an annular nut above said force distribution ring, said nut having a threaded engagement with said shell, and said nut having a lower end in abutment with said force distribution ring to place pressure simultaneously on said upper shoulder of said insulator and on said powder when said nut is turned downwardly.

4. A spark plug comprising an outer metal shell having an external thread near its firing end to engage a spark plug opening in a wall of a chamber containing gases under high pressures, said shell also having a central passage therethrough, a second thread near the end of said shell opposite said firing end, an insulator extending substantially through said passage and having a lower shoulder for. transferring abutment force to said shell shoulder, said insulator also having an upper shoulder, said upper shoulder facing opposite said lower shoulder and sloping downwardly and radially outwardly, a body of packing powder in said pocket, an annular force distribution ring above said upper shoulder and said powder with the radially inner portion of said annular ring arranged to apply compressive force to said insulator and the radially outer portion of said annular ring arranged'to apply compressive force to said powder, a sealing ring closing of the bottom of said pocket beneath said powder, and a nut above said force distribution ring, said not having a thread engaged with said second thread of said shell, and said nut having a lower end sloping downwardly and radially outwardly to engage said force distribution ring with the bottommost portion of said nut being positioned over said powder, whereby said nut acts to compress said powder and toforce said insulator into operative abutment with said shell shoulder.

5. The spark plug of claim 4 wherein said force distribution ring has a tapered outer edge which closely fits the sidewalls of said central passage over said body of powder.

6. A spark plug comprising an outer metal shell having an external thread near its firing end to engage a spark plug opening in a wall of an engine cylinder containing gases under high pressure, said shell also having a central passage therethrough, a second thread near the end of said shell opposite said firing end, said shell having a shoulder in said passage near said external thread, an insulator extending substantially through said passage and having a lower shoulder for transferring abutment force to said shell shoulder, said insulator also having an intermediate shoulder and an upper shoulder, said intermedaite and upper shoulder facing opposite said lower shoulder and forming a pocket between said shoulders with said shell, said upper shoulder sloping downwardly and radially outwardly toward said pocket, a gasket between said shell shoulder and said lower shoulder of said insulator, a sealing ring at the bottom of said pocket above said intermediate shoulder, a body of packing powder in said pocket above said sealing ring, a packing ring disposed above staid powder, an annular force distribution ring above said upper shoulder and said packing ring, the radially inner portion of said annular ring being arranged to apply compressive force to said insulator and the radially outer portion of said annular ring arranged to apply compressive force to said packing, and a nut above said force distribution ring, said nut having a thread engaged with said second thread of said shell, and said nut having a lower end that slopes downwardly and radially outwardly to engage said force distribution ring with the bottommost portion of said not being positioned over said 5 6 packing, whereby the powder is confined to said pocket 2,020,967 11/1935 Rohde 174-152 and compressive force is applied to said gasket through 2,193,392 4/ 1940 Twining et 1 5 said powder and said insulator.

References Cited by the Examiner FOREIGN PATENTS UNITED STATES PATENTS 5 985,492 3/1951 France- 1,776,424 9/ 1930 Eyquem LARAMIE E. ASKIN, Primary Examiner. 2,020,965 11/1935 Rohde 313-144 X 

3. A SPARK PLUG COMPRISING: AN OUTER METAL SHELL HAVING A CENTRAL PASSAGE THERETHROUGH, SAID SHELL HAVING A SHOULDER IN SAID PASSAGE NEAR THE LOWER END, AN INSULATOR EXTENDING SUBSTANTIALLY THROUGH SAID PASSAGE AND HAVING A LOWER SHOULDER FOR TRANSFERRING ABUTMENT FORCE TO SAID SHELL SHOULDER, SAID INSULATOR ALSO HAVING AN UPPER SHOULDER FACING OPPOSITE SAID LOWER SHOULDER, SAID INSULATOR AND SHELL FORMING A POCKET POSITION BELOW SAID UPPER SHOULDER AND WHICH POCKET IS SUBSTANTIALLY CLOSED AT ITS LOWER END, A BODY OF PACKING POWER IN SAID POCKET, AN ANNULAR FORCE DISTRIBUTION RING ABOVE SAID UPPER SHOULDER AND OVERLYING SAID POWER WITH THE RADIALLY INNER PORTION OF SAID ANNULAR RING ARRANGED TO APPLY COMPRESSIVE FORCE TO SAID INSULATOR AND THE RADIALLY OUTER PORTION OF SAID ANNULAR RING ARRANGED TO APPLY COMPRESSIVE FORCE TO SAID POWER, A SEALING RING CLOSING OFF THE BOTTOM OF SAID POCKET BENEATH SAID POWDER, AND AN ANNULAR NUT ABOVE SAID FORCE DISTRIBUTION RING, SAID NUT HAVING A THREADED ENGAGEMENT WITH SAID SHELL, AND SAID NUT HAVING A LOWER END IN ABUTMENT WITH SAID FORCE DISTRIBUTION RING TO PLACE PRESSURE SIMULTANEOUSLY ON SAID UPPER SHOULDER OF SAID INSULATOR AND ON SAID POWDER WHEN SAID NUT IS TURNED DOWNWARDLY. 